This invention relates to a magnetic fuel injection valve for internal combustion engines and, more particularly, to a fuel injection valve which employs a globe valve for improving an atomization fuel injection.
The conventional magnetic fuel injection valve using a globe valve as a valve disk has an advantage over a pintle type fuel injection valve in that there is a greater allowance for the inclination of the valve disk relative to the valve seat. This greater allowance permits reduction in machining accuracy of valve housing and, therefore, the reduction in the manufacturing cost while at the same time reducing the weight of the moving parts including the valve disk so as to result in an improvement in the response speed of the valve disk. However, a disadvantage of the conventional fuel injection valve resides in the fact that it is difficult to work on the globe valve to increase the diffusing angle of fuel spray and, consequently poor fuel atomization results.
A fuel injection valve is known in which the fuel is supplied at high speed from the inlet orifice into a vortex chamber, with the inlet orifice being cut through the valve housing from the external surface to the inner surface in a direction tangent to an outer surface of the glove valve. The vortex chamber is enclosed by a inner surface of the valve housing, an outer surface of the globe valve and the valve seat, so that the supplied fuel swirls in the vortex chamber to increase the diffusing angle of the fuel spray injected out of the outlet orifice. In this fuel injection valve, since the fuel circles or swirls around upstream of the valve seat, the apparent flow coefficient at the valve seat is small, so that it is necessary to increase the valve stroke to obtain the fuel passage area at the valve seat. However, increasing the valve stroke results in an increase in the time it takes for the globe valve to travel through the full stroke. This time increase increases the speed at which the moving unit, made up of the globe valve, plunger and rod, strikes against the stopper, with the resulting rebounding movement making the amount of fuel injection unstable. A further disadvantage of this fuel injection valve resides in the fact that, if the fuel is metered by the outlet orifice, the fuel remaining in the vortex chamber just prior to the opening of the valve flows out of the outlet orifice without being swirled thereby resulting in the apparent orifice flow coefficient becoming greater than in the normal condition. This flow of fuel remaining in the vortex chamber causes an excess amount of fuel to be injected when the valve begins to open, making it difficult to control the fuel flow in the small fuel flow range. When the fuel is metered by the inlet orifice, usually three or more inlet orifices are required to be arranged in parallel to ensure a uniform atomization. However, the provision of three or more inlet orifices and requires a reduction in a diameter of the inlet orifices and consequently highly accurate machining. Yet another fuel injection valve is known wherein a spiral member is provided downstream of the valve seat to increase the diffusion angle of fuel spray. In this fuel injection valve, the fuel is given a swirling motion at the downstream side of the valve seat, so as to avoid the above noted disadvantage. However, a disadvantage of this known fuel injection valve resides in the fact that since the fuel is supplied from the opposite side of the valve seat, the fuel must flow through the center of the coil, the fuel passage in the plunger and around the globe valve to reach the valve seat thereby creating a flow resistance. Therefore, when the valve is open, the fuel pressure immediately upstream of the valve seat decreases, reducing the flow speed of the fuel passing through the fuel passage groove resulting in an insufficient diffusing angle of fuel spray at the start of fuel injection. Another disadvantage of this kwown fuel injection valve resides in the fact that because the glove valve is not guided, the movement of the valve is unstable.